In recent years, valve open/close timing control devices that make it possible to change the opening/closing timing of an intake valve and an exhaust valve in accordance with the operation status of an internal combustion engine (hereinafter referred to as an “engine” as well) have been put to practical use. These valve open/close timing control devices have a mechanism that, for example, by changing the relative rotation phase of the driven rotating body with respect to the rotation of the driving rotating body (hereinafter referred to as simply “relative rotation phase”) by means of an engine operation, changes the opening/closing timing of an intake/exhaust valve that is opened and closed accompanying the rotation of the driven rotating body.
In general, the optimal opening/closing timing of the intake/exhaust valve differs according to the operation state of the engine, such as the state in which the engine is started, and the state in which the vehicle is traveling. By constraining the relative rotation phase to a predetermined phase between the maximum retard phase and the maximum advance phase when starting the engine, the opening/closing timing of the intake/exhaust valve that is optimal for starting the engine is realized, and a case in which a knocking sound is generated due to a partition of a fluid pressure chamber formed by the driving rotating body and the driven rotating body swinging is suppressed. For this reason, it is desired that the relative rotation phase is constrained to a predetermined phase before the engine is stopped.
PTL 1 discloses a valve open/close timing control apparatus that can lock the relative rotation phase in an intermediate lock phase based on an engine stop signal. In this valve open/close timing control apparatus, advancing control, retarding control, intermediate phase holding control, and lock control for locking in the intermediate lock phase are performed by one hydraulic control valve (electromagnetic valve). These controls are performed by changing the position of a spool in the hydraulic control valve according to an amount of electricity supplied to a solenoid. Specifically, (1) a case in which “total draining”, “locking in an intermediate lock phase by means of an advancing action”, “an advancing action in an unlocked state”, “intermediate phase holding”, and “a retarding action in an unlocked state” are controlled in the stated order, and (2) a case in which “a retarding action in an unlocked state”, “intermediate phase holding”, “an advancing action in an unlocked state”, “locking in an intermediate lock phase by means of an advancing action”, and “total draining” are controlled in the stated order, as the amount of electricity supplied to the solenoid increases from 0, are disclosed.